By using atomic layer-by-layer oxide molecular beam epitaxy, Sr-δ-doped La₂CuO₄ (LCO) multilayered structures, in which some atomic layers of LaO have been fully substituted by SrO layers, have been fabricated. By varying the spacing between the LCO and SrO layers high-T_c superconductivity (≈ 40 K) has been obtained. The local variation of in-plane and out-of plane atomic lattice parameters and the strontium redistribution in multilayers grown on a LaSrAlO₄ (LSAO) substrate are investigated in this study. more

Cu(In,Ga)Se₂ (CIGSe) based solar cells fabricated with multi-stage co-evaporation show power-conversion efficiencies of more than 20%. However, in some cases efficiencies fall below this value, in particular when the solar cell is manufactured using low-temperature processing without a Cu-rich stage. The reasons for this efficiency loss, as well as the limitations for further efficiency increase, are not fully understood. In this project, we analyse structural defects in CIGSe absorber layers to gain a better understanding of the defects’ chemical characteristics. more

Oxide materials exhibit a wide range of ionic and electronic phenomena such as superconductivity, magnetism, ferroelectricity, thermoelectricity, etc. The crystal structure of oxides (generally perovskite or a derivative) is highly adaptable to changes in composition and this compatibility provides the opportunity of combining multiple oxides into heterostructures. Our aim is to reveal the atomic and electronic structure of the heterostructure interfaces using various Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) techniques. more

CeO₂ and Y₂O₃-stabilized zirconia (YSZ) are two candidates for electrolyte materials in solid oxide fuel cells because of their high ion conductivities. Recent experiments have shown that hetero-structures consisting of alternating layers of Gd-doped CeO₂ and YSZ exhibit even higher ionic conductivity than either of the bulk materials. In this project, we investigate the structure and chemistry of interfaces between CeO₂ and YSZ using scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS). more